The present invention is intended for use in the manufacture of armatures of the type having an armature core and a commutator mounted in spaced relation on an armature shaft and wherein the commutator is provided with coil lead-receiving hooks or tangs. As used herein, the term "start wires" refers to the wire segments (also called "coil leads") leading to the first coils wound by the fliers. The term "finish wires" refers to the wire segments or coil leads extending from the last coils wound. In double flier armature winding machines having two fliers, there are two start and two finish wires.
Flier-type armature winding machines commonly have a commutator shield assembly including an inner shield and an outer shield. The inner shield is notched to expose a pair of commutator tangs to enable lead wires to be connected to them. When coils are being wound by the fliers, the outer shield covers the commutator tangs exposed through the inner shield notches to prevent the wire segments extending from the fliers from engaging the aforementioned commutator tangs. The outer shield is retracted from the path of the wire segments when the lead wire connections between the coil leads and the commutator tangs are to be made, as by reverse and forward movements of the fliers. Thus, coil lead connections to the tangs can be made by manipulation of the outer shield and the fliers.
In a typical process for winding an armature, the end of a wire segment extending from a flier is held by a wire gripper or clamp and the wire segment is looped around a commutator tang, after which the short strand of wire between the tang and the wire gripper is severed as close to the tang as possible. Coil lead connections between subsequently wound coils are made between the finish of the winding of one coil and the start of the winding of the next coil. A finish wire extending from the last coil to be wound by each flier is looped about the appropriate tang, the wire segment extending from that tang to the flier is clamped by the wire gripper or clamp, and the wire severed as closely as possible to the same tang. In a double flier armature winder, the foregoing process is carried out simultaneously by both fliers using duplicate sets of wire grippers and duplicate sets of wire cutters.
U.S. Pat. No. 3,812,577, granted to Jerry L. Compton and David R. Seitz on May 28, 1974, discloses an approach to the severing of the coil lead wires from an armature while it is located in a winding machine wherein either one or both of the start and finish wires are severed by relative movement of the wire clamps gripping the wires and the armature. As a result of such relative movement, the wires are stressed at the tangs and severed at or quite near the edges of the tangs. Accordingly, there is little excess wire left extending from the tangs and further trimming operations are unnecessary.
The approach disclosed in said Compton et al. '577 patent is frequently used, especially for relatively fine wire applications wherein there is a relatively high probability that the wire will break at the edge of the tang. There are circumstances in which start wires connected to tangs in accordance with the teachings of said Compton et al. '577 patent may be pulled off the tangs when the fliers commence rotation to wind the first coils. This problem may be cured in many cases by looping each start wire two times around its associated tang in the manner described in U.S. Pat. No. 3,713,208, granted to James N. Doyle on Jan. 30, 1973. However, it is not always desirable to employ the methods of said Doyle '308 patent due to the geometry of the commutator tangs. For example, a tang may be so configured that the additional start wire loop has an adverse effect upon the connection of the finish wire or upon the subsequent processing of the armature, such as the usual hot-staking or fusing of the tangs and the wire loops. Occasionally, wires severed from tangs in accordance with said Compton et al. '577 patent break at locations between the tangs and the wire clamps in which event the excess wire lengths must be manually trimmed. This can present a costly and difficult manufacturing problem when using modern high speed production equipment. In other cases, especially with relatively heavy wire, tangs may be bent when the clamps are moved to sever the wires.
A method and apparatus proposed to address the problems discussed above is disclosed in U.S. Pat. No. 4,633,577, issued to Alvin C. Banner on Jan. 6, 1987. With the mechanism shown in the Banner '577 patent, a pair of wire trimming members having sharp edges that may be located close to a pair of diametrically opposed tangs are provided, each of which is supported by an arm pivotally mounted on a part fixed in relation to the inner shield. A driving connection in the form of a pin and a cam slot is provided between each arm and the outer shield whereby each arm is caused to pivot in response to movements of the outer shield. Wire clamps that grip the wires are moved away from the trimming members whereupon the wires are pulled against and severed at the trimming edges because of the high stress concentration experienced by the wires at that point. The concept of breaking lead wires across the edges of trimming members is employed by the apparatus of this invention, and the Banner U.S. Pat. No. 4,633,577 is incorporated by reference herein.
The mechanism shown in the Banner '577 patent has not proved to be satisfactory because it is difficult to adjust and maintain in adjustment in addition to being relatively complex and space-consuming. Moreover, there is a tendency for the wires to be scraped or torn by the trimming edges rather than to be cleanly broken.
U.S. Pat. No. 5,379,511, issued to Nathan A. Corey, Carl L. Clark, and Patrick A. Dolgas on Jan. 10, 1995, discloses a method and an apparatus that overcomes the deficiencies noted above with regard to the Banner '577 patent. The Corey et al. U.S. Pat. No. 5,379,511, which is incorporated by reference herein, discloses severing a start or finish wire closely adjacent its associated commutator tang by positioning a wire trimming blade closely adjacent to the outer periphery of the inner shield and substantially parallel to the longitudinal axis of an armature in the winding station. The trimming blade is mounted on a mounting bracket for pivotal or rocking movement about a pivot axis extending transversely through the blade and intermediate its ends. At its forward end, the trimming blade has a sharp end edge termed a "trimming edge".
When the outer shield is retracted to expose a pair of tangs, the trimming blade shown in the Corey et al. '511 patent is pivoted, by engagement therewith of a cam bearing member on the outer shield, into a position in which its forward end extends through a blade-receiving notch in the forward end of the inner shield and its wire trimming edge is located in a wire-severing position at or closely adjacent to a commutator tang and closer to the armature shaft than the outermost surfaces of the tangs. This locates the trimming blade so that a start or finish wire can be pulled over a portion of a trimming edge and severed closely adjacent the tang about which the start or finish wire is looped or hooked. The actual severing of a wire lead is accomplished by pulling the wire segment leading to the wire clamp or gripper against the sharp trimming edge by moving the wire gripper away from the armature core.
Severing coil leads in accordance with the Corey et al. '511 patent as well as severing coil leads in accordance with the other aforementioned methods and apparatus severs the wire sufficiently close to the tang for many applications. However, other applications require still closer start and finish wire trimming to produce acceptable parts.